"I have a horn in my pocket,

up through our two plate glass skylights: but as always they were completely opaque, covered with a thick coating of rime and dusting of snow. I looked away from the skylights across to where Joss, our young Cockney radioman, was stirring uneasily in his sleep, then back to Jackstraw. "Still hear it?" "Getting louder all the time, Dr Mason. Louder and closer." I wondered vaguelyvaguely and a trifle irritably, for this was our world, a tightly-knit, compact little world, and visitors weren't welcomewhat plane it could be. A met. plane from Thule, possibly. Possibly, but unlikely: Thule was all of six hundred miles away, and our own weather reports went there three times a day. Or perhaps a Strategic Air Command bomber testing out the DEW-linethe Americans' distant early warning radar systemor even some civilian proving flight on a new trans-polar route. Or maybe some base plane from down by Godthaab. "Dr Mason!" Jackstraw's voice was quick, urgent. "It's in trouble, I think. It's circling uslower and closer all the time. A big plane, I'm sure: many motors." "Damn!" I said feelingly. I reached out for the silk gloves that always hung at night above my head, pulled them on, unzipped my sleeping-bag, swore under my breath as the freezing air struck at my shivering skin, and grabbed for my clothes. Half an hour only since I had put them off, but already they were stiff, awkward to handle and abominably coldit was a rare day indeed when the temperature inside the cabin rose above freezing point. But I had them onlong underwear, woollen shirt, breeches, silk-lined woollen parka, two pairs of socks and my felt cabin shoesin thirty seconds flat. In latitude 72.40 north, 8000 feet up on the Greenland ice-cap, self-preservation makes for a remarkable turn of speed. I crossed the cabin to where no more than a nose showed through a tiny gap in a sleeping-bag. "Wake up, Joss." I shook him until he reached out a hand and pushed the hood off his dark tousled head. "Wake up, boy. It looks as if we might need you." "Whatwhat's the trouble?" He rubbed the sleep from his eyes and stared up at the chronometer above his head. "Midnight! I've been asleep only half an hour." "I know. Sorry. But get a move on." I recrossed the cabin, passed by the big RCA transmitter and stove, and halted in front of the instrument table. The register showed the wind ENE, velocity 15 knotsnear enough 17 miles per hour, on a night like this, with the ice-crystals and compare nikon and canon digital cameras drift lifting off the ice-cap, clogging and slowing up the anemometer cups, the true speed was probably half as much again. And the pen of the alcohol thermograph was running evenly along the red circle of 40 degrees below zero72 degrees of frost. I thought of the evil combination of these two factors of wind and cold and felt my skin crawl. Already Jackstraw was silently climbing into his furs. I did the samecaribou trousers and parka with reindeer fur trimmed hood, all beautifully tailored by Jackstraw's wifesealskin boots, woollen mittens and reindeer gloves. I could hear the plane quite clearly now, and so too, I could see, did Joss. The deep even throb of its motors was plain even above the frantic rattling of the anemometer cups. "It'sit's an aeroplane!" You could see that he was still trying to convince himself. "What did you think it wasone of your precious London double-deckers?" I slipped snow-mask and goggles round my neck and picked up a torch from the shelf beside the stove: it was kept there to keep the dry batteries from freezing. "Been circling for the past two or three minutes. Jackstraw thinks it's in trouble, and I agree." Joss listened. "Engines sound OK to me." "And to me. But engine failure is only one of a dozen possible reasons." "But why circle here?" "How the devil should I know? Probably because he can see our lightsthe only lights, at a guess, in 50,000 square miles. And if he has to put down, which God forbid, he stands his only chance of survival if he puts down near some human habitation." "Heaven help them," Joss said soberly. He added something else, but I didn't wait to hear. I wanted to get up top as quickly as possible. To leave our cabin, we had to use a trap-door, not an ordinary door. Our cabin, a prefabricated, sectioned structure that had been hauled up from the coast on tractor sleds during the month of July, was deep-sunk in a great oblong hole that had been gouged out from the surface of the ice-cap, so that only the top few inches of its flat roof projected above ground level. The trap-door, hinged at both ends so that it could open either upwards or downwards, was reached by a short steep flight